Update electron statuses for `AWSLambdaExecutor`

Once separation of workflow and electron statuses is done, the electron level statuses need to be updated to accommodate executor dependent statuses. In this case the following status definitions will be updated:

- `REGISTERING` - Uploading task and registering the function

- `PENDING_BACKEND` - Corresponds to lambda function state `Pending`

- `RUNNING` - Corresponds to Lambda function state `Active`

- `COMPLETING` - Lambda function is in the inactive state, result files being retrieved, temporary files are being deleted

For the end state, there is a separate class called `EndState` and contains all possible end state statuses like `COMPLETED`, `FAILED`, etc. and thus does not need to be added to the executor dependent status.

Acceptance Criteria:

- [ ] Above mentioned statuses need to be updated inside the local executor
- [ ] Tests need to be added to verify if those definitions are as expected

Start by locating the local executor and its current status definitions, then review the existing test structure. Update the executor-dependent statuses to match the four specified meanings and add tests verifying those definitions; completion is reached when the tests pass and end-state statuses remain in EndState.

Written by the indexing model from the issue text.